1. Field of the Invention
The present invention relates to electromagnetic parts for use in electrical equipment by making use of electromagnetic action.
2. Description of the Prior Art
Electromagnetic parts for use in electrical equipment such as motors, generators, and transformers are formed by winding a winding around a magnetic core.
For instance, shown in FIGS. 8 to 10 is a stator of a motor as an example of such electromagnetic parts. The core 1 in this case employs a laminated core formed by cylindrically laminating a thin silicon steel sheet. In addition, the core 1 has slots 3, 3 . . . longitudinally thereof for housing windings 2, 2 . . . which are wound to surround magnetic poles 4, 4 . . . formed among the slots 3, 3 . . . .
Prior electromagnetic parts employ the so called enamel wire as the wirings 2, 2 . . . , the enamel wire being yielded by coating a surface of a copper wire with a coating of insulating resin. For the enamel wire, one having PVF called Formal wire or Formex wire baked thereon is widely employed, and in particular when electromagnetic parts are employed at higher temperature, a heat resisting enamel wire on which epoxy resin and silicon resin or polyimide resin, etc. baked thereon is employed.
Such an enamel wire is, since likely to be damaged, enclosed with an insulating cover 5 or an insulating sheet 6 substantially made of resin and mica, etc., and housed in the slots 3, 3 . . . . These windings 2, 2 . . . are connected to each other as needed in the electromagnetic parts, from which lead wires 7, 7 . . . are taken out for connection with a power source (not shown). As the lead wires 7, 7 . . . , a resin coated wire is typically employed. Nowadays, various vacuum appratus are widely employed in various fields such as for example, energy and medical treatment, etc., as well as in industry. To drive and control, or measure any equipment in such a vacuum apparatus, the need to employ an electical equipment such as motors, linear actuators, and generators has been increased.
However, in evacuating gases from such a vacuum apparatus to a vacuum, particularly to a high vacuum more than 10.sup.-3 Torr or a ultra-high vacuum more than 10.sup.-7 Torr, gas molecules such as air absorbed in a substance are released into the vacuum. This causes some troubles in that foreign molecules are mixed in the vacuum. Accordingly, for electrical equipment to be employed in a vacuum, they must be subjected to heat treatment called baking where they are previously exposed to temperature from 350.degree. to 400.degree. C. for evaporating adsorbed gases.
However, prior electromagnetic parts which use an enamel wire as the windings 2, 2 . . . are applicable only at temperature of 300.degree. C. or less even if a heat resisting one is employed therefor. Accordingly, the baking can not be applied thereto.
Moreover, heat radiation due to convention in the atomosphere can substantially not be anticipated in a vacuum, so that, when employing any electical equipment therein, electromagnetic parts included therein reaches high temperature of several hundred degrees Celsius owing to heat dissipation from the electric resistance of the windings 2, 2 . . . and eddy-current loss, etc. produced in the core 1. Under such a situation, baked resins and the like, which are difficult to be evaporated in the atmosphere, are also evaporated and released in the vacuum vessel as molecules thereof.
Accordingly, it is actually impossible to employ in a vacuum prior electromagnetic parts using an enamel wire as the windings 2, 2 . . . .
As a result, a prior vacuum apparatus was adapted to remotely incorporate needed power externally of the vacuum vessel via a link such as a shaft and an arm, etc.